head to study of harvard estimates that iraq and afghanistan together will be the most expensive wars in u.S. History, costing $6 trillion, including care for veterans when they come home. And tonight, abc's chief global affairs correspondent martha raddatz, who has spent years covering the troops on the ground, is back in afghanistan, and she is there with the general who is going to guide america's exit. Reporter: I have traveled thousands of miles with almost every commanding general here over the years, all trying to win this war, but this trip across afghanistan was different. Unlike all others. General joseph dunford is charged with ending america's longest war. While so many wonder why we are still here, the view from our v-22 osprey, with flares for protection from missile fire, is a reminder that much work still needs to be done. What are we doing here? We are working on the afghan national security forces. We are developing their capabilities so they can provide security here in afghanistan. Reporter: And they are not ready yet? And they are not ready yet. Reporter: Not ready now but dunford is confident that by the end of 2014, when america's combat role here ends, they will be. And what does that look like? We saw it today, at this remote combat outpost in southern afghanistan, that has seen some of the toughest fighting in the war. Afghan security forces today officially took over. More than 120 u.S. Soldiers who have vacated in recent days helped turn this district around. But not without a price. And there are some very sad reminders of the losses here. Yeah. You're the first one going home? Yes. All right. Take care. Reporter: So, what worries you most about this place? The lack of confidence and the uncertainty that are felt by the afghan people. I think the taliban will attempt to feed those fears about the post-2014 environment. confidence in the afghan forces, general d dunford believes that americans will be needed to stay behind here to ensure the gains and sacrifices of the past 11-plus years, are not lost. Martha raddatz, abc news, helmand province.

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